I own one and have used it extensively.
It is sharp as a tack, very fast and takes lovely pictures. I personally prefer the 105 length for macro because I shoot a lot of bugs, and you don't have to get as close (i.e. disturb them... and their stingers) as much. Having said all of that, there are a couple of things you should know about the lens.
First, it hunts a lot in AF mode, in macro. I mean, it hunts a LOT. The two position focus limiter switch is (in my mind) configured all wrong, it should be configured to .5 meters or less, or long... this would keep it from hunting as much as it does. Some people this REALLY bothers, but I never use auto focus when shooting macro anyway, so I personally don't care much about that.
Second, the VR part of it works well... but as you close in on a subject, the VR deteriorates... you can get 3-4 stops when shooting longer things with the lens (portraits), but when you get in close it only gives you about 1 stop effectiveness... and it needs to be turned off on the tripod.
Third, the lens is listed as a 2.8, but keep in mind that (like just about all modern macros) it really is a variable aperture lens, going up to about 3.5 when you change the focus level.
Ok, don't misunderstand me here, the lens takes amazing pictures... the resolution it can do far exceeds the digital cameras I have it on... but if you are thinking that this is the perfect lens to run around at dusk taking bug pictures on autofocus, shooting handheld with VR, then I think you will be disappointed.
On a tripod, with manual focus, it can't be beat for image quality.
Having said that, if you are going to shoot that way why not save yourself $300 or so dollars and buy the previous non-vr version of this same lens slightly used? If I had to do it all over again, that is what I would do.
I do find myself pulling this out of the bag a lot just to use it as a medium telephoto prime on my D80, however, because it is an uncommonly sharp, very fast prime and the VR works wonders in low light for portraits and general shooting.